Structure for foundry slurry viscosity reduction

ABSTRACT

Structure for and the method of decreasing the viscosity of foundry sand additive slurries by the use of up to 3 percent of sodium silicate or potassium silicate in the foundry sand additive slurries to provide a workable slurry having a high percentage of solids therein for foundry sand requiring a high ratio of additives to water for proper tempering and rebonding thereof.

United States Patent 91 [111 3,910,564

Graham et a1. Oct. 7, 1975 ['54] STRUCTURE FOR FOUNDRY SLURRY 3,448,967 6/1969 Seanor 259/154 VISCOSITY REDUCTION 3,463,461 8/1969 Kirk I r 3,719,214 3/1973 Erndt 259/154 [75] Inventors: Alexander L. Graham, Livonia;

RobertL. Cleland, Albion, both of Mich Przmary Exammer-Robert W. Jenkins Attorney, Agent, or Firm-Whittemore, Hulbert & [73] Assignee: Harry'W. Dietert C0., Detroit, g k

Mich.

[22] Filed: Apr. 17, 1972 ABSTRACT [21] Appl. No.: 244,420

Structure for and the method of decreasing the VISCOS- ity of foundry sand additive slurries by the use of up to [52] U.S. Cl. 259/154 3 percent f Sodium Silicate or potassium silicate in [51] Int. Cl. B28C'7/04 the f d Sand additive slurries to provide a work- [58] Fleld of Search 259/154, 149, 161, 162, able Slurry having a high percentage f Solids therein I 259/163 164, 1663 168 for foundry sand requiring a high ratio of additives to i water for proper tempering and rebonding thereof. [56] References Cited UNITED STATES PATENTS 9 Claims, 1 Drawing igu 3,110,421 11/1963 Matthias 259/154 46 56 PROPORTION/IL 4O 1 RESOLVER 42 SODIUM OR DRY 54 POTASSIUM ADDITIVES V 1 SILICATE 9 VISCOSITY 3 D RECEIVER VISCOSITY I0 SENSOR 32 ADDITIVE TRANSMITTER SLURRY MIXER [2 H AGITATOR |/5s la US. Patent Oct. 7,1975

STRUCTURE FOR FOUNDRY SLURRY VISCOSITY REDUCTION BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to tempering and rebonding of foundry sand and refers more specifically to structure for and a method of tempering and rebonding foundry sand with additives in a water slurry to which a viscosity reducing agent has been added whereby the solids to liquids ratio of a pumpable slurry may be increased.

2. Description of the Prior Art In the past, tempering and rebonding of foundry sand has often been accomplished by the use of dry additives such as bentonites, seacoal and cellulose flour in addition to water which have been separately placed in a foundry sand mixer. It has been found that if the additives are mixed with the tempering water prior to their introduction into the foundry sand mixer so that the additives are allowed to presoak, the rehydration of the additive clay so accomplished is beneficial in the tempering operation. The use of such a slurry in particular reduces the loss of dry additives and fines due to ventilation of the mixer during the cooling cycle.

It has, however, in the past been found that slurry sand conditioning systems are faced with limitations. Thus, for example, with western bentonite additives a clay level of about 9 percent by weight in the slurry can produce a slurry viscosity too high to permit convenient handling. So-called high viscosity bentonites can form thixotropic gels at clay levels as low as 8 percent.

Also, foundry sand being conditioned may require an addition of as much as 0.2 to 0.3 percent of clay, while requiring only a small amount of water to allow for evaporation while the sand is being cooled and to bring the moisture content of the mixed sand back to the required level. It is necessary, therefore, that a slurry be provided having a'high enough solids to-water ratio to satisfy the additive need without exceeding the water requirement of the sand to be conditioned.

Some slurrics with high viscosity and low solids content -are incapable of fully conditioning foundry sand under specific conditions because of the low solids-towater ratio, and the slurry must be supplemented with dry additives. To make slurry systems more widely applicable and to make present slurry systems more practical, it is desirable to reduce the slurry viscosity so that higher solids-to-water ratios are possible.

SUMMARY OF THE INVENTION In accordance with the present invention, sodium silicate and/or potassium silicate are used as viscosity control agents for foundry slurries. Up to 3 percent of the sodium silicate and/or potassium silicate are dispersed in the water which is then mixed with sand additives such as sodium and calcium bentonites to effect a solids-to-water ratio increase of up to 22 percent.

In a practical application, an additive slurry having a high solid-to-water ratio is prepared by mixing dry additives with water to which l percent by weight of the dry additives of sodium or potassium silicate has been added, after which the viscosity of the slurry so pro- BRIEF DESCRIPTION OF THE DRAWING The drawing is a diagrammatic representation of sand conditioning structure including a slurry additive system constructed in accordance with the invention for practicing the method of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in the drawing, the sand conditioning structure 10 includes a mixer 12 for mixing foundry sand, water and additives to condition the foundry sand, a source 14 of the foundry sand to be conditioned, a source of tempering water 16 including metering valves 24 and 26, a slurry additive system 18 including metering valve 30 and slurry pump 29 and, if desired, additional additive structure 20 including valve 28. As shown, the conditioned sand from the mixer 12 may be removed from the area of the mixer on the conveyor 22.

The mixer 12, foundry sand source 14 and tempering water source 16 are known structure and will not therefore be considered in detail herein. Similarly, the additional additive structure 20 and the conveyor 22 may be of any convenient design known in the foundry industry.

The slurry additive system 18, however, in accordance with the invention includes the slurry tank 32 in which dry additives, water and viscosity reducing agents are mixed by agitator 33 in accordance with the invention.

Water is supplied to the additive slurry tank 32 from a conventional water source 34 through metering valve 44. Sodium or potassium silicate is added to the tank 32 from the sodium or potassium silicate source 40 through the metering valve 42. Similarly, dry additives such as sodium and/or calcium bentonites are added to the slurry tank 32 from the dry additive source 36 through metering valve 38 and holding tank or hopper 39.

It will be understood that valves 38 and 42 as well as the water valve 44 may be manually actuated if desired.

In accordance with the invention it is desirable to add up to for example 3 percent of sodium or potassium silicate for a western bentonite dry additive to produce an additive slurry having a workable viscosity with up to 22 percent more solids therein than is possible without the addition of the sodium or potassium silicate.

While the sodium and potassium silicate may be added to the slurry by manual operation of the valve 42, for example, if desired, proportional resolvers are available which will meter a predetermined percent of the dry additives passing through valve 38 of the sodium or potassium silicate through the valve 42.

Further, it has been found that it is desirable to first add for example a fixed percentage as for example 1 percent by weight of the dry additives of sodium or potassium silicate to the water before the additives are dispersed in the water to form the sluffy and to subse quently add an additional amount as for example another 2 percent of the dry additives by weight of the sodium or potassium silicate to the slurry in accordance with the viscosity of the slurry produced by the addition of the first 1 percent of sodium or potassium silicate to the dry additive and water slurry.

If the dry additives are added to the water before the first 1 percent of sodium or potassium silicate, the resulting mixture may become sticky and mixing of the sodium and potassium silicate therewith at a later date may become difficult or impossible. After the addition of the first 1 percent of the silicate to the water, the resulting mixture including the dry additives readily accepts the additional silicates.

Accordingly, a viscosity sensor transmitter 48 is shown in conjunction with the slurry tank 32 for sensing the viscosity of the slurry in the tank 18 and a viscosity receiver 50 is shown connected between the viscosity sensor transmitter and the valve 42 for controlling the valve 42 in accordance with the viscosity sensed by the viscosity sensor transmitter.

In one particular embodiment of the invention a Milton Roy controlled volume pump was used as the valve 42, which pump was manually set for the percentage of silicate to be added and the pump operation automatically timed based on the weight of bentonite to be addedto the slurry tank by the operation of the proportional resolver 46. The pre-measured additives were then released from the hopper 39 into the slurry tank 32 after the entry of the silicate into the tank.

In the same embodiment the controlled volume pump was automatically adjusted in accordance with the viscosity of the slurry in tank 32 by the use of a Brookfield Viscometran Capacitance Viscosity Transmitter and a Foxboro Viscosity Receiver which controlled the air pressure supplied to the controlled volume pump actuator.

While specific commercially available structure is thus recited for the proportional resolver 46, the viscosity sensor and transmitter 48, viscosity receiver 50 and the pump 42, it will be understood that other commercially available equipment, and indeed equipment which it is within the skill of the art to design which is not commercially available, may be used to practice the invention.

In overall operation of the sand conditioning structure illustrated, the foundry sand from the foundry sand source 14 is tested to determine the amount of additives and water required to temper the sand in the mixer. The dry additives and water from the sources 36 and 34 are added to the additive slurry tank 32 through the valves 38 and 44 and the hopper 39 either manually or automatically following a predetermined percent of sodium or potassium silicate added to tank 32 from the source 40 through the valve 42.

Particularly if the addition of the sodium or potassium silicate is automatic, 1 percent by weight of the dry additives of the sodium or potassium silicate is first added to the water in the slurry tank 32 under for example the control of the proportion resolver 36, followed by the release of the premeasured additives in the holding hopper 39. The viscosity of the slurry in the tank 32 is then sensed and an additional amount of sodium or potassium silicate is added to the additive slurry in the tank 32 in accordance with the sensed viscosity of the slurry to produce a slurry having a particularly high solids content.

When the additional sodium or potassium silicate is added automatically, the viscosity of the slurry in the tank 32 is sensed by means of the viscosity sensor transmitter 48 and the valve 42 is controlled by the viscosity receiver 50 connected between the transmitter 48 and valve 42.

While one embodiment of the present invention has been considered in detail, it will be understood that other embodiments and modifications thereof are contemplated. It is the intention to include all such embodiments and modifications within the scope of the invention as are defined by the appended claims.

What we claim as our invention is:

1. Structure for producing foundry sand additive slurry comprising an additive slurry tank, means operably associated with the slurry tank for first adding water to the slurry tank, means operably associated with the slurry tank for determining the amount of a viscosity reducing agent to be initially added to the water in the additive slurry tank as a proportion of dry additive to be added to the water in the additive slurry tank, means for then metering the viscosity reducing agent into the water in the additive slurry tank, and means for feeding the amount of dry additives into the additive slurry tank.

2. Structure for producing foundry sand additive slurry comprising an additive slurry tank, means operably associated with the slurry tank for adding water to the slurry tank, means operably associated with the slurry tank for adding a dry additive to the slurry tank, means operably associated with the slurry tank for metering a viscosity reducing agent for the dry additive and water in the slurry tank into the tank, and means operably associated with the slurry tank and the means for adding a dry additive to the slurry tank for adding a first fixed percentage of the dry additive by weight of the viscosity reducing agent to the water in the slurry tank before the dry additive enters the water in the slurry tank so that a high percentage of solids may be present in the slurry in the tank for a given slurry viscosity and tempering of foundry sand or the like may be accomplished with the slurry even though the foundrysand may require a high percentage of additives in relation to the tempering water required thereby.

3. Structure as set forth in claim 2 wherein the dry additive is a bentonite and the viscosity reducing agent is one of sodium and potassium silicate.

4. Structure for producing foundy sand additive slurry comprising an additive slurry tank, means operably associated with the slurry tank for adding water to the slurry tank, means operably associated with the slurry tank for adding a dry additive to the slurry tank,

means operably associated with the slurry tank for metering a viscosity reducing agent for the dry additive and water in the slurry tank into the tank, means for adding a first fixed percentage of the dry additive by weight of the viscosity reducing agent to the water in the slurry tank before the dry additive enters the water in the slurry tank, and means for subsequently adding an additional amount of viscosity reducing agent to the slurry in accordance with the viscosity of the slurry having the first fixed percentage of the viscosity agent added thereto.

5. Structure as set forth in claim 4 wherein the dry additive is a bentonite and the viscosity reducing agent is one of sodium and potassium silicate.

6. Structure as set forth in claim 4 wherein the means for adding an additional amount of sodium or potassium silicate to the slurry comprises a viscosity sensor transmitter for providing a signal proportional to the viscosity of the slurry and a viscosity receiver for controlling the additional amount of sodium or potassium silicate in accordance with the sensed viscosity of the slurry.

7. Structure for producing foundry sand additive slurry comprising an additive slurry tank, means operably associated with the slurry tank for adding water to the slurry tank, means operably associated with the slurry tank for adding a dry additive to the slurry tank, means operably associated with the slurry tank for metering a viscosity redu'cingagent for the dry additive and water in the slurry tank into the tank, and means for first adding 1 percent by weight of the dry additive of the viscosity reducing agent to the water used in forming the additive slurry and means for subsequently adding an additional amount up to 2 percent of the viscosity reducing agent to the additive slurry in accordance with the viscosity of the additive slurry to which the initial 1 percent of the viscosity reducing agent has been added so that a high percentage of solids may be present in the slurry in the tank for a given slurry viscosity and tempering of foundry sand or the like may be accomplished with the slurry even though the foundry sand may require a high percentage of additives in relation to the tempering water required thereby.

8. Structure as set forth in claim 7 wherein the dry additive is at least one of sodium and calcium bentonite and the viscosity reducing agent is one of sodium and potassium silicate.

9. Structure for producing foundry sand additive slurry comprising an additive slurry tank, means operably associated with the slurry tank for first adding water to the slurry tank, means operably associated with the slurry tank for determining the amount of viscosity reducing agent to be initially added to the water in the slurry tank as a proportion of the dry additive to be added to the water in the additive slurry tank, means for then metering the viscosity reducing agent into the water in the additive slurry tank, means for feeding the amount of dry additives into the additive slurry tank, means for sensing the viscosity of the mixed water, dry additive and viscosity reducing agent in the additive slurry tank operably associated with the additive slurry tank, and means operably associated with the viscosity sensing means for metering an additional amount of viscosity reducing agent into the additive slurry tank in accordance with the viscosity of the slurry in the slurry tank up to a maximum of 2 percent by weight of the dry 

1. Structure for producing foundry sand additive slurry comprising an additive slurry tank, means operably associated with the slurry tank for first adding water to the slurry tank, means operably associated with the slurry tank for determining the amount of a viscosity reducing agent to be initially added to the water in the additive slurry tank as a proportion of dry additive to be added to the water in the additive slurry tank, means for then metering the viscosity reducing agent into the water in the additive slurry tank, and means for feeding the amount of dry additives into the additive slurry tank.
 2. Structure for producing foundry sand additive slurry comprising an additive slurry tank, means operably associated with the slurry tank for adding water to the slurry tank, means Operably associated with the slurry tank for adding a dry additive to the slurry tank, means operably associated with the slurry tank for metering a viscosity reducing agent for the dry additive and water in the slurry tank into the tank, and means operably associated with the slurry tank and the means for adding a dry additive to the slurry tank for adding a first fixed percentage of the dry additive by weight of the viscosity reducing agent to the water in the slurry tank before the dry additive enters the water in the slurry tank so that a high percentage of solids may be present in the slurry in the tank for a given slurry viscosity and tempering of foundry sand or the like may be accomplished with the slurry even though the foundry sand may require a high percentage of additives in relation to the tempering water required thereby.
 3. Structure as set forth in claim 2 wherein the dry additive is a bentonite and the viscosity reducing agent is one of sodium and potassium silicate.
 4. Structure for producing foundy sand additive slurry comprising an additive slurry tank, means operably associated with the slurry tank for adding water to the slurry tank, means operably associated with the slurry tank for adding a dry additive to the slurry tank, means operably associated with the slurry tank for metering a viscosity reducing agent for the dry additive and water in the slurry tank into the tank, means for adding a first fixed percentage of the dry additive by weight of the viscosity reducing agent to the water in the slurry tank before the dry additive enters the water in the slurry tank, and means for subsequently adding an additional amount of viscosity reducing agent to the slurry in accordance with the viscosity of the slurry having the first fixed percentage of the viscosity agent added thereto.
 5. Structure as set forth in claim 4 wherein the dry additive is a bentonite and the viscosity reducing agent is one of sodium and potassium silicate.
 6. Structure as set forth in claim 4 wherein the means for adding an additional amount of sodium or potassium silicate to the slurry comprises a viscosity sensor transmitter for providing a signal proportional to the viscosity of the slurry and a viscosity receiver for controlling the additional amount of sodium or potassium silicate in accordance with the sensed viscosity of the slurry.
 7. Structure for producing foundry sand additive slurry comprising an additive slurry tank, means operably associated with the slurry tank for adding water to the slurry tank, means operably associated with the slurry tank for adding a dry additive to the slurry tank, means operably associated with the slurry tank for metering a viscosity reducing agent for the dry additive and water in the slurry tank into the tank, and means for first adding 1 percent by weight of the dry additive of the viscosity reducing agent to the water used in forming the additive slurry and means for subsequently adding an additional amount up to 2 percent of the viscosity reducing agent to the additive slurry in accordance with the viscosity of the additive slurry to which the initial 1 percent of the viscosity reducing agent has been added so that a high percentage of solids may be present in the slurry in the tank for a given slurry viscosity and tempering of foundry sand or the like may be accomplished with the slurry even though the foundry sand may require a high percentage of additives in relation to the tempering water required thereby.
 8. Structure as set forth in claim 7 wherein the dry additive is at least one of sodium and calcium bentonite and the viscosity reducing agent is one of sodium and potassium silicate.
 9. Structure for producing foundry sand additive slurry comprising an additive slurry tank, means operably associated with the slurry tank for first adding water to the slurry tank, means operably associated with the slurry tank for determining the amount of viscosity reducing agent to be initially Added to the water in the slurry tank as a proportion of the dry additive to be added to the water in the additive slurry tank, means for then metering the viscosity reducing agent into the water in the additive slurry tank, means for feeding the amount of dry additives into the additive slurry tank, means for sensing the viscosity of the mixed water, dry additive and viscosity reducing agent in the additive slurry tank operably associated with the additive slurry tank, and means operably associated with the viscosity sensing means for metering an additional amount of viscosity reducing agent into the additive slurry tank in accordance with the viscosity of the slurry in the slurry tank up to a maximum of 2 percent by weight of the dry additive. 